Optoelectronics packaging is one of the most difficult and costly operations in optoelectronics manufacturing. Optoelectronic packages provide submicron alignment between optical elements, high-speed electrical connections, excellent heat dissipation, and high reliability. Providing such features has resulted in optoelectronic packages that may be larger, costlier and more difficult to manufacture than electronic packages. In addition, current designs of optoelectronic packages and associated fabrication processes are ill adapted for automation because today's high-performance butterfly packages are characterized by a large multiplicity of mechanical parts (submounts, brackets, ferrules, etc.), three-dimensional (3D) alignment requirements, and poor mechanical accessibility.
For manufacturers, the trends driving the demand for new optical packaging are providing an opportunity for reducing the cost of developing 10 Gbps application technology and a challenging market increasingly characterized by a diversity of applications. Consequently, manufacturers need an approach to component-level packaging that can be applied to both transmitter and receiver modules and to various products and applications without the need for a full redesign of each new component package. Within such an approach, manufacturers should be able to precisely align a laser chip or photodiode to single-mode fiber with high coupling efficiency and maintain this alignment, meet the RF (radio frequency), thermal, and hermetic sealing requirements and provision them for direct integration into the package for cost, space, and power savings; and simultaneously develop a low-cost automation capability for easily scalable manufacturing.
Of particular concern is the RF emission requirements. RF emissions are produced in varying degrees by virtually every type of electrical equipment. Electromagnetic shielding may be used to protect electrical equipment from this unwanted electromagnetic radiation or EMI. Many systems require at least some shielding for proper operation or to meet RF requirements for emissions and immunity. As circuit speeds and sensitivities increase so will the need for improved shielding.
Electromagnetic shielding often provides protection for electrical equipment by reducing unwanted signals to levels that do not adversely affect equipment. This is achieved by both reflecting and absorbing the radiation signals. Reflection depends on a permeability and conductivity of the shielding material, and a frequency and wave impedance of the signal. Generally, the reflectance of a shielding material increases with frequency. The remaining signal passing through a shielding material is reduced by absorption. The resistivity and thickness of the shield, effects absorption.
However, while shielding may protect RF emissions from radiating outside of a shielded module, it does little to protect other potentially sensitive components within the module or which may be radiated out of the module via an input or output lead which may act as an antenna to radiate RF emissions past the shield. Thus, rather than simply shielding, it may be desirable to reduce the overall RF emissions produced by a component.